Blue print machine



March 19, 1935. H. J. BRUNK BLUE PRINT MACHINE 2 sheets sneet 1 FiledMay 28, 1952 min W paw/g March 19, 1935. H. J. BRUNK BLUE PRINT MACHINEFiled May 28, 1932 2 Sheets-Sheet 2 liwen/or' 9 a4 wla AIl3/ju/L/ i 7Patented Mar. 19, 1935 PATENT OFFICE 1,99s.199 BLUE PRINT MACHINE HaroldJ. Brunk, Chicago, Ill., assignor to The C. F. Peace Company, acorporation of Delaware Application May' 28, 1932, Serial No. 614,152

5 Claims.

This invention relates to improvements in blue print machines and in themethod of developing the blue prints and so-called white prints, 1. e.,prints having blue lines on a white background.

Ordinarily blue print paper is coated with a solution containingmixtures of potassium ferricyanide and organic salts of iron such asferric ammonium oxalate. During the period of exposure to this light thepotassium ferricyanide is partly reduced to potassium ferrocyanide whilethe ferric ammonium oxalate is reduced to ferrous ammonium oxalate.

After exposure, the paper is washed with clear water which removes allthe unexposed chemicals from the areas which were behind the opaqueportion of the tracing or other negative and also removes the looseexposed or reduced chemicals 1. e., that portion which does not adhereto the fibres of the paper. This washing,

,in a certain sense, also starts the process of oxidation of the reducedchemical which action is necessary in the formation of the blue lines orareas. In other words, if left long enough in the water the so-calledpotash treatment herein- 25 after referred to, is unnecessary. It is theprac tice, however, to complete the oxidation by applying potassiumbichromate or some other strong oxidizing agent to the surface of thepaper immediately after the application of the first 30 water wash. Theexcess bichromate or so called potash must be washed off the surface byapplying a second water wash, after which the paper is ready for drying.

Prints made in this manner are far from'satisfactory or dependable whenfirst class blue prints with clear white lines or blue line prints on a.clear white background are desired. The cumculties may be analyzed asfollows:

When making blue line prints or blue lines on a white background fromnegatives of tracings, the fully exposed chemical in the area outside ofor between negatives runs down into the white background and stains itblue immediately when waters is applied to the surface of the paper.

The blue lines themselves at certain exposures run down into the whiteground giving them a ragged appearance.

In the case of blue prints, or white lines on a blue ground (which areobtained when a tracing or positive original is used) the blue in theground runs over the line giving it a bluish cast and at the same timeclosing up on the line making it narrower than the line the originaltracing and at full exposures of e blue ground the line may be lostcompletely.

Various methods of washing have been tried with the idea of preventingthis running or (bleeding mentioned above but none has proven successfulheretofore. No method of changing the application of water is successfulbecause 5 the bleeding is caused by the formation of insoluble Prussianblue when the unexposed chemi cal on the print mixes with or combineswith the exposed orreduced portions. The Prussian blue formed, runs intothe white and cannot be 10 washed out, once it stains the print. Fromthis it is evident that moisture applied to the paper in a quantitysufiicient to remove the surplus chemical, regardless of how applied, isbound to cause the exposed chemical to mix with the 15 unexposedportion, as nothing separates the two, and even if the blue formed isnot in sufficient quantities to run very far, the line itself will beunsatisfactory.

The object of the present invention is to pro- 20 vide a. machine fordeveloping prints of this character without the objectionable running orbleeding of the color, regardless of the speed of operation of the blueprint machine or of the length of exposure, and which also results inthe production of clear white full lines on blue prints, a perfectlywhite background on blue line prints, a deep Prussian blue followingfull exposures and one which does not fade readily,

a wide range of exposure without the need of many different printingspeeds and the successful printing from tracings or from negativeswithout changing the speed.

A contributory object is to provide an improved printing and developingmachine in which the foregoing advantages are attained by developing thepaper immediately after printing and before any water has been appliedto the surface, after which the prints are washed and may then betreated with an oxidizing agent in the usual way and then dried.

An additional object is to provide equipment for developing blue printsin this manner, comprising an attachment for continuous blue printmachines, such as are now on the market.

Otherwise expressed, the present invention is directed to sensitizingpaper with ferric compounds, exposing the sensitized paper to a sourceof light with portions of the surface shielded from the source of lightwhereby the compounds of the exposed portion of the sensitized paper arereduced to a ferrous state, thereafter treating the paper with adeveloper containing ferric compounds adapted to render insoluble thereduced ferrous compounds and then washing the paper so treated withwater. Preferably the ferric compounds of the developer are of the samechemical characteristics as the ferric compounds used to sensitize thepaper and in fact some of the identical coating compounds, washed fromthe paper, may be used as the developer, thus economizing in the use ofthe developing solution;

A further object of the invention therefore is to provide means forcollecting the unexposed developer, washed from the paper and applyingit to said paper as a developing solution or as supplementing saiddeveloping solution, whereby the initial supply of developer may be usedalmost indefinitely.

In the accompanying drawings I have illustrated two differentembodiments of the inven tion.

Fig. 1 is a side elevation .of a complete print-- ing, developing anddrying machine.

Fig. 2 is an elevation of the opposite end of the developing attachment.v

Fig. 3 is a section, somewhat diagrammatic, of a modified form ofdeveloper applying mechanism, by means of which the developer may beused repeatedly.

The frame of the machine 10 is similar to that of a well-known type ofprinting, washing and drying machine now on the market and since much ofthe mechanism used is the same as in said commercial machine, except forthe means forapplying the developing solution between the printing stageand the water washing stage, said machine will be described verybriefly.

The sensitized paper is supported on a suitable roller 11, at one end ofthe machine, said paper 12 being drawn past a sheet of curved glass 13,where it is exposed to a suitable source of ligl (preferably a row ofarc lights) in a well-known manner, the paper leaving the printingsection of the machine where it passes over a roller 14' and thereafterunder a roller 15, rotatable on a shaft, the ends of which arecarried inblocks 15 secured to vertical, parallel chains 15. Thus said roller isfree to move up and down, its weight being supported by the loop ofpaper as shown, thereby maintaining the proper tension on the paper andproviding for expansion and contraction of the same.

The paper then passes the means for applying the developer which mayhave the form of a roll 16 dipping in a pan 1'7 containing thedeveloping solution, supplied by a suitable reservoir 18. This roll, panand associated parts may be in the form of an attachment, readilyapplicable to existing machines.

From the developer the paper travels past the first water washconsisting of a tube 19 with suitable nozzles which direct sprays ofwater against the inclined surface of the paper in a manner which hasbeen used heretofore, the paper thereafter travelling over suitablerollers to the potash roller 20 which dips in a pan 21, supplied withbichromate of potash or other suitable oxidizing agent, contained in areservoir 22. paper then travels upwardly past the final water wash, thewater being supplied from the pipe 23, and thereafter passes through thedryer 24 where it is dried in the usual manner, and thereafter wound ona removable roller 25.

The paper used is sensitized with a ferricyanide and, after exposure, areducing agent is used to convert the ferricyanide to ferrocyanide. Thereducing agent at the same time is capable of forming with the reduced.ferrocyanide a blue precipitate (Prussian blue) having high tinc- The.

torial value. Any diffusion of the reduced ferrocyanide into theunexposed portions, such as would result in the formation of the sameprecipitate in the unexposed portions, is prevented by fixing, i. e,,precipitating said reduced ferrocyanide prior to washing with water.

A practical sensitizing formula is as follows: Potassium ferricyanide, 5pounds in 5 gallons of water. Ferric ammonium oxalate, 34 pounds in 12gallons of water. Ammonium oxalate, 1 pounds in 4 gallons of water. Mixthe above to.- gether making a. total batch of 21% gallons of solution.

An appropriate developer for the above would be: 1 pound potassiumferricyanide in 1 gallon of water. 51/ pounds ferric ammonium oxalate in2 gallons of water. Mixing together gives 3 gallons of developer.

The photochemical reaction consists in the reduction of ferricyanide toferrocyanide by the conjoint action of sunlight and a photo sensitivereducing agent, as for example, an organic ferric salt broadly and, morespecifically, ferric ammonium oxalate. There is no useful reactionbetween a ferric salt and a ferricyanide but cyanide was reduced toferrocyanide and the ferric salt to ferrous salt in the exposedportions, and upon treatment with'wash water a migration or bleedingtook place, resulting in an impairment or destruction of the highlydesirable sharp definition between the exposed and unexposed portions.

The procedure described prevents the combination on paper of (l) theferrous ammonium oxalate and potassium ferricyanide that was not exposedto the light, in the course of printing, and (2) the potassiumferrocyanide with any ferric ammonium oxalate that was not exposed tolight in the course of printing. After developing as above, the printsare washed in a clear water wash and then completely oxidized withpotassium bichromate or other agent, as previously stated, and thesurplus can then be washed off and the prints ready for drying.

The machine and process operate to prevent migration or diffusion byfixing the reduced ferrocyanide before washing the paper. By this fixingprocess the 'ferrocyanide is rendered insoluble and incapable ofreacting with the ferric salt in the unreduced portions. In those casesWhere a ferric organic salt is employed as the photosensitive lucingagent and is itself reduced to the ferrous condition, the fixingsolution should also contain an agent, as for example a ferricyanide, tofix'the ferrous salt and prevent it from diffusing and combining withferricyanide in the unexposed portions.

Tests have been. made with alarge number of possible developersincluding all of the common ferric compounds and most of the rare andother metallic salts, from which the following show possibilities asdevelopersi Potassium ferricyanide; ferric ammonium oxalate; ferricammonium citrate; ferric sodium oxalate; ferric chloride; ferricpotassium oxalate"; and sodium perborate.

The potassium ferricyanide and the ferric ammonium oxalate incombination are by far the best and the potassium ferricyanide workswell alone on the slower printing papers. The relative amount ofpotassium ferricyanide and ferric ammonium oxalate can be changed togive dif- .tainer 37 from which ferent shades of blue, the deeper shadesof blue being obtained when the relative amounts of potassiumferricyanide in the sensitizing formula and in the developing solutionbalance. For example, a fast printing paper has less potassiumferricyanide in the formula than a slow printing paper; therefore, lessshould be used in the developing solution.

In addition to potassium bichromate other oxidizing agents may be used,such as other bichromates, hydrogen dioxide, sodium perborate, potassiumpersulphate, and potassium ferricyanide. It is understood that the useof any of these agents follows the washing of the paper.

In the form of developing apparatus shown in Fig. 3 as a modification ofthe developer applying portion of the machine first described (or as anattachment) the sensitized paper 25 is fed into the machine with thetracings or other negatives laid on it in the usual manner so that asthe paper travels past the curved sheet of glass 26, it is exposed tothe usual bank of arc lamps 27. The paper is carried along by an endlessbelt 28 passing over supporting rollers 29 and 30 from which said paperpasses under roller 31 the weight of which is supported in part by theloop of paper as shown and as previously described in connection withthe corresponding roller '15 in Fig. 1. The span of paper then travelsupwardly over roller 32, under roller 33,

extends diagonally downwardly to the water wash described in connectionwith Fig. 1.

The developer is supplied to a suitable conit flows through a pipe 38 toa pump 39 of any suitable form'such as a centrifugal pump shown andwhich is operated by a shaft 40, the developer being pumped upwardlythrough the pipe 41 to the transverse discharge pipe 42 from which it isdischarged through a series of orifices against the roll 33, forming apuddle 43 between the roll and the downwardly travelling span ofsensitizedtpaper. This arrangement insures the necessary contact betweenthe paper and the developing solution, the developer, or the majorportion of it, thereafter flowing downwardly over the paper in thesubstantiallyvertical span between roll 34 and 35 and collecting in afurther puddle 44 between the lower roller and the loop of paper, theexcess developer running off near the ends thereof and being caught in apan 45 with a discharge outlet 46 through which it is returned to thereservoir 37. Such film of developing solution as tends to adhere to thevertically moving span of paper between rolls 35 and 36 also flowsdownwardly forming a puddle tween the paper and the roller and is draineback into the reservoir 3'7.

The developing solution not only develops the exposed reduced portionsof the sheet but also serves to wash offtor remove the unexposed portionof the coating compound, which, as previously stated, is very similar toor may be identical with the developing solution itself, so that thedeveloper is used over and over and increases in concentration as thedeveloping. operation continues. During long continued operation, thedeveloper may be diluted by-adding small quantities of water from timeto time to the reservoir 37, without exercising any great amount of careas to the precise amount added, as reasonable variations inthe watercontent do not appreciably aflfect the developing operation. Therelatively long loop of paper depending from the rolls 34 and 36, isprovided to give a sumcient length of wash not only to enable thedeveloping solution to properly perform its developing function but moreparticularly to insure removal of the unexposed chemicals from thepaper.

It will be understood that the preferred coating formula set out hereinin conjunction with the preferred developing solution has been selectedwith particular reference to producing the desired shade of blue and toinsure a very desirable contrast between the blue and the white portionsof the finished print. These preferred formulae are particularly usefulin making ordinaryblue prints wherein almost the entire surface coatingis exposed and reduced, the only unexposed portions being the linescorresponding to the lines on the tracing, which lines in the aggregateconstitute only a small fraction of the total area of the print. In suchprints the blue background, of course, predominates and it is verydesirable, therefore, that the proper shade of blue be obtained.

In making blue line prints, however, where most of the print ismasked bythe negative and only a small area is exposed to the light and thusreduced, resulting in blue lines on a white back ground, it is lessimportant to produce the same shade of blue as in the case of ordinaryblue prints, and therefore in developing blue line prints the developingsolution may be any one of a number of standard solutions used incoating blue print paper. In fact, it is to be understood that theformulae given herein do not differ gr:atly from standard coatingsolutions in their essential ingredients but have been developed asrefinements for the purpose of giving the improved results heretoforepointed out.

In view of the foregoing, it will be apparent that where the machine isused exclusively or at least for considerable intervals of time inmaking 'blue line prints or so-called white prints, the

operation may be started by using nothing but clear water in the supplytank and after running possibly 25 yards or more of the blue print paperthrough the machine, sufllcient chemical solution will have collected inthe supply tank to permit the operation to continue in the mannerheretofore described, i. e. the print produced will be ing the developeras the machine may be oper ated in the ,usual way from the outset andthe clear water pumped from the developer tank will act in the same wayas the usual water wash and produce blue prints, or more particularly,blue line prints, of the same character now produced under prevailingmethods. In other words, the prints initially produced will not have auniformly sharp definition but as the operation progresses, they willimprove in this respect until the machine is operating entirely inaccordance with the improved process.

The prints resulting from the new process constitute a remarkableimprovement over blue prints, white prints and the like made by theprevailing method, in that there is no at any speed or exposure, theblue prints show clear white full lines on a deep Prussian bluebackground, the blue line prints show a perfectly white background, thedeep blue color fades slower than the present shades of blue whenexposed to sunlight, and there is a wide range of exposure permissiblewhich eliminates the need of providing sensitized papers with variousdifferent' printing speeds.

This application is a continuation in part of my application Serial No.536,378, Blue prints and process of making the same, filed May 11, 1931,and issued May 31, 1932, as Patent No. 1,861,298. Said patent claims themethod of producing nonbleeding photo-prints. The claims of the presentapplication are directed to the apparatus.

. I claim:

1. A machine for making blue prints comprising, a developing section fora strip of blue print paper and means for conveying said blue printpaper through the same, said developing section having a developerapplying station and a roller at a lower elevation around which saidpaper passes from the higher station whereby the developer flowsdownwardly and collects between said roll and said span, a reservoir"beneath said roll, for collecting the developer flowing from the endsof said roll and means for recirculating said developer from saidreservoir to said first station.

2. A machine of the class described for developing blue prints,comprising a developing section, means for moving a sheet of blue printpaper past the same, said developing section comprising an upper and alower roll around which said blue print paper passes, means fordirecting liquid developer against said upper roll to provide a puddleof developer between said roll and the approaching span of said sheet,said lower roll being positioned to cause a similar puddle of developerto form from the developing solution flowing down said sheet, areceptacle for receiving developer discharged from said lower roll andmeans for redelivering developer from said receptacle to said developerdirecting means.

3. A machine of the class described comprising past said sections, saidzones being spaced sufficiently with respect to the rate of travel ofsaid sheet through the same to aiford adequate time to develop theexposed portions of the chemical on said sheet and toremove theunexposed portions thereof prior to washing.

4. In a blue print machine, a reservoir for a developer, means forsupporting a sheet of sensitized paper and causing it to travel in aloop, means adjacent said loop and connected to said reservoir fordirecting said developer against the inside surface of the upper part ofsaid loop, whereby said developer will run down to the bottom ofsaid'loop and collect therein, means for collecting the developerdrained from said loop and delivering it to said reservoir, and meansfor subsequently applying water to said developed sheet, said meanscomprising the only water supply for said sheet to that point in itstravel.

5. Developing apparatus for blueprint machines, comprising two rollsfrom which a loop of blue print paper may depend, a third roll at thebottom of said loop, a discharge pipe for developernear the top of saidloop and on the side I of the paper corresponding to the inside of saidloop, whereby said developer flows down the inner surface ofv one spanof said loop to the bottom thereof, a pan to collect the developerdrained from said loop, a reservoir, and a pump connected to saidreservoir and to said discharge pipe.

HAROLD J. BRUNK.

